This is a 52-week study of children with advanced HIV infection and their response to drug combinations, including zidovudine (AZT, ZDV), didanosine (ddI), zalcitabine (ddC), stavudine (d4T), lamivudine (3TC), nevirapine (Virarume), ritonavir (Norvir), and nelfinavir (Viracept). All drugs except nevirapine and ddC have been FDA approved for use in children. Two hundred children will participate nationwide and 8 children locally. Drugs are taken for 52 weeks, and if tolerated, patients are offered an option for an additional 48 weeks of therapy. Study endpoints include: a) lack of viral load suppression (RNA PCR), i.e., < 0.75, b) treatment safety, and c) performance of pharmacokinetics (PK) of study drug combinations. Secondary endpoints include study of specific characteristics of HIV RNA changes (slope, nadir, AUC, etc.), CD4 change, weight change, population PK and survival comparisons.